microcom: add new applet, this time for real

diff --git a/util-linux/microcom.c b/util-linux/microcom.c
new file mode 100644 (file)
index 0000000..f6f8e07
--- /dev/null
+++ b/util-linux/microcom.c
@@ -0,0 +1,135 @@
+/* microcom.c
+ *
+ * bare bones 'talk to modem' program - similar to 'cu -l $device'
+ * inspired by mgetty's microcom
+ *
+ */
+#include "busybox.h"
+
+int microcom_main(int argc, char **argv);
+int microcom_main(int argc, char **argv)
+{
+       struct pollfd pfd[2];
+#define sfd (pfd[1].fd)
+       char *device_lock_file = NULL;
+       const char *s;
+       const char *opt_s = "9600";
+       unsigned speed;
+       int len;
+       int exitcode = 1;
+       struct termios tio0, tiosfd, tio;
+
+       getopt32(argv, "s:", &opt_s);
+       argc -= optind;
+       argv += optind;
+       if (!argv[0])
+               bb_show_usage();
+       speed = xatou(opt_s);
+
+       // try to create lock file in /var/lock
+       s = bb_basename(argv[0]);
+       if (!s[0]) {
+               errno = ENODEV;
+               bb_perror_msg_and_die("can't lock device");
+       }
+       device_lock_file = xasprintf("/var/lock/LCK..%s", s);
+       sfd = open(device_lock_file, O_CREAT | O_WRONLY | O_TRUNC | O_EXCL, 0644);
+       if (sfd < 0) {
+               if (ENABLE_FEATURE_CLEAN_UP)
+                       free(device_lock_file);
+               device_lock_file = NULL;
+               if (errno == EEXIST)
+                       bb_perror_msg_and_die("can't lock device");
+               // We don't abort on other errors: /var/lock can be
+               // non-writable or non-existent
+       } else {
+               // %4d to make mgetty happy. It treats 4-bytes lock files as binary,
+               // not text, PID. Making 5+ char file. Brrr...
+               s = xasprintf("%4d\n", getpid());
+               write(sfd, s, strlen(s));
+               if (ENABLE_FEATURE_CLEAN_UP)
+                       free((char*)s);
+               close(sfd);
+       }
+
+       // open device
+       sfd = open(argv[0], O_RDWR | O_NDELAY);
+       if (sfd < 0) {
+               bb_perror_msg("can't open device");
+               goto unlock_and_exit;
+       }
+       fcntl(sfd, F_SETFL, O_RDWR); // why?
+
+       // put stdin to "raw mode", handle one character at a time
+       tcgetattr(STDIN_FILENO, &tio0);
+       tio = tio0;
+       tio.c_lflag &= ~(ICANON|ECHO);
+       tio.c_iflag &= ~(IXON|ICRNL);
+       tio.c_oflag &= ~(ONLCR);
+       tio.c_cc[VMIN] = 1;
+       tio.c_cc[VTIME] = 0;
+       if (tcsetattr(STDIN_FILENO, TCSANOW, &tio)) {
+               bb_perror_msg("can't tcsetattr for %s", "stdin");
+               goto unlock_and_exit;
+       }
+
+       /* same thing for modem (plus: set baud rate) - TODO: make CLI option */
+       tcgetattr(sfd, &tiosfd);
+       tio = tiosfd;
+       tio.c_lflag &= ~(ICANON|ECHO);
+       tio.c_iflag &= ~(IXON|ICRNL);
+       tio.c_oflag &= ~(ONLCR);
+       tio.c_cc[VMIN] = 1;
+       tio.c_cc[VTIME] = 0;
+       cfsetispeed(&tio, tty_value_to_baud(speed));
+       cfsetospeed(&tio, tty_value_to_baud(speed));
+       if (tcsetattr(sfd, TCSANOW, &tio)) {
+               bb_perror_msg("can't tcsetattr for %s", "device");
+               goto unlock_and_exit;
+       }
+
+       // disable SIGINT
+       signal(SIGINT, SIG_IGN);
+
+       // drain stdin
+       tcflush(STDIN_FILENO, TCIFLUSH);
+       printf("connected to '%s' (%d bps), exit with ctrl-X...\r\n", argv[0], speed);
+
+       // main loop: check with poll(), then read/write bytes across
+       pfd[0].fd = STDIN_FILENO;
+       pfd[0].events = POLLIN;
+       /*pfd[1].fd = sfd;*/
+       pfd[1].events = POLLIN;
+       while (1) {
+               int i;
+               while (-1 == poll(pfd, 2, -1) && EINTR == errno)
+                       continue;
+               for (i = 0; i < 2; ++i) {
+                       if (pfd[i].revents & POLLIN) { 
+                               len = read(pfd[i].fd, bb_common_bufsiz1, COMMON_BUFSIZE);
+                               if (len > 0) {
+                                       if (!i && 24 == bb_common_bufsiz1[0])
+                                               goto done; // ^X exits
+                                       write(pfd[1-i].fd, bb_common_bufsiz1, len);
+                               }
+                       }
+               }
+       }
+ done:
+       tcsetattr(sfd, TCSANOW, &tiosfd);
+       tcsetattr(STDIN_FILENO, TCSANOW, &tio0);
+       tcflush(STDIN_FILENO, TCIFLUSH);
+
+       if (ENABLE_FEATURE_CLEAN_UP)
+               close(sfd);
+       exitcode = 0;
+
+ unlock_and_exit:
+       // delete lock file
+       if (device_lock_file) {
+               unlink(device_lock_file);
+               if (ENABLE_FEATURE_CLEAN_UP)
+                       free(device_lock_file);
+       }
+       return exitcode;
+}